Morphological diversity in humeral remains from a South African Konzentrat‐Laggerstätte site provide new insights into the Early Triassic archosauromorph radiation

The end-Permian mass extinction event was the largest faunal mass extinction in the history of life on Earth. Understanding the recovery of terrestrial diversity in the Early Triassic is confounded by a global scarcity of continental fossil-bearing deposits of this time frame. This is especially problematic for vertebrate paleontology because the clade encompassing living birds, crocodiles, and turtles (the Archosauromorpha) is hypothesized to undergo a rapid radiation at this time. The Langbergia-Garjainia Subzone (LGSz) of South Africa represents one of the few highly fossiliferous Early Triassic (Olenekian) localities worldwide. However, only one archosauromorph taxon is described from this site to date, the large-bodied Garjainia madiba. Here, we assess a newly discovered assemblage of fragmentary archosauromorph humeri from localities in Driefontein 11 revealing an impressive diversity of minimally six taxa. These include non-archosauriform archosauromorphs, non-archosaurian archosauriforms, and crown archosaurs, mirroring the contemporaneous diversity seen in Laurasian deposits. Importantly, we identify among this sample potentially the first records of azendohsaurids and aphanosaurs from South Africa. The archosauromorph assemblage from the LGSz displays a wide array of body sizes and anatomical characteristics. These findings further support mounting evidence to Early Triassic origins of the archosauromorph evolutionary radiation.